A proportional-integral-derivative (PID) controller is a common feedback loop component in industrial control applications. The PID controller is composed of a proportional unit, an integral unit and a derivative unit, and is thus capable of performing proportional, integral and/or derivative operations for error signals. Adjustments made to a proportional parameter Kp, an integral parameter Ki and a derivative parameter Kd (or adjustments made to other similar parameters) of the PID controller may be intuitively reflected on a response behavior (e.g., a response time or a steady-state error) of the system. By designing and fine-tuning the parameters Kp, Ki and Ki of the PID controller, users are able to adjust a control system to satisfy design requirements. Therefore, the PID controller is applied in industrial manufacturing processes to control basic loop (e.g., control gas pressure, fluid temperature, flow rate, liquid level, boiler combustion, etc.).
When the parameters Kp, Ki and Ki of the PID controller are adjusted improperly, the PID controller cannot reach a rated performance, resulting in poor control loop performance. Poor control loop performance can directly or indirectly affect product quality in production line and can also result in waste of energy use to thereby increase production cost. The parameter tuning method of the PID controller may be roughly divided into two categories, in which one is known as the rule based method and another one is known as the optimization algorithm based method. The rule based method has a simple tuning process, where a parameter of the PID controller may be calculated through a specific formula derived simply by substituting some known parameters (e.g., a system gain, a time constant, and a delay time) of a controlled system into a mathematic structure of the controller. The optimization algorithm based method adopts a numerical computation to find the parameter matching a specific performance specification by performing a parametric searching after adding restricted conditions (control performance specification) into a parametric model.
However, regardless of whether the rule based method or the optimization algorithm based method is adopted to perform the parameter tuning of the PID controller, it is required to know a control algorithm (e.g., a PID calculation formula being used) of the PID controller to be adjusted. The control algorithm is provided by the controller manufacturer. The PID controllers with different brands or model numbers may use different PID calculation formulas (control algorithms), and/or use different parameter definitions. The manufacturer may provide a PID parameter tuning software suitable for its own PID controller, so that the parameter of the PID controller may be calculated according to the specific performance specification. In general, when the PID parameter tuning is to be performed on basis of the optimization algorithm based method, three information items first be known of, which are: a mathematic model (system model) of a system to be controlled (target system), a calculation formula (control algorithm) of a known PID controller and a control performance specification (specific performance specification) that the user planned to achieve. According to the system model, the control algorithm (calculation formula) of the known PID controller and the specific performance specification of the design requirements, the PID parameter tuning software can perform the optimization algorithm to find an optimal parameter matching the specific performance specification.
Since different manufacturers may adopt different PID calculation formulas (control algorithms), in order to expand an applicable range of the software, developers of the PID parameter tuning software need to improve the software supportability by establishing an algorithm database corresponding to different controllers. However, the PID parameter tuning software cannot be used in cases where brand name or model number of the PID controller is unknown, or said brand name or model number are known but the controller is not supported.